Efforts to develop cardiac prostheses and support devices have been ongoing for many years, with notable success in certain respects. Such activities can generally be categorized as directed either to the provision of an implantable replacement heart, or of an external unit for temporary bypass of, or assistance to, the natural organ. Although the present invention appertains to a heart pump that is intended primarily to serve the latter functions, the concepts involved may indeed have more universal applicability.
It has, in any event, been recognized in the art that the manner in which such an artificial pump effects blood flow is of crucial importance to its feasibility, simulating as closely as possible the operation of the corporeal heart. Thus, the unit must be so designed as to permit continuous, uninterrupted inflow, under the influence of virtually no negative pressure. These conditions avoid the imposition of unnatural loads upon the vascular system of the subject, and permit an inherent balance to be established between the systemic and pulmonary circuits. Moreover, the discharge from the pump must be of a pulsitile nature, to ensure effective dispersion of the blood throughout all vessels of the body.
The foregoing principles have been enunciated in U.S. Pat. No. 3,518,033 to Andersen, who discloses an extracorporeal heart which consists essentially of lengths of normally flat rubber tubing associated with a valve structure. The arrangement is such that an artificial atrium and ventricle chamber are defined in adjacent portions of the tubing, by sequential operation of two valve structures. While the Andersen device endeavors to incorporate principles that are necessary to the provision of a successful mechanical heart pump, it nevertheless suffers from serious deficiencies. In particular, to ensure utmost effectiveness and reliability, it is highly desirable that a unit of this sort be as simple as possible, whereas the two-chamber arrangement and the drive and valving system utilized by Andersen is quite complex. Moreover, such a device would require relatively high levels of operating force, and the simultaneous actuation of both halves of the system (simulating the two sides of the heart), as taught by Andersen, are similarly undesirable. While the art proposes a wide variety of cardiac devices, some of which may avoid certain deficiencies that can be identified in the Andersen unit, it is not believed that there has heretofore been proposed a heart pump having those features which are optimal for utmost effectiveness and feasiblity .
Accordingly, it is a primary object of the present invention to provide a mechanical heart pump which is simple and reliable, and which operates with a continuous, uninterrupted and non-sucking inflow characteristic, and a pulsatile discharge of the blood.
It is also an object of the invention to provide such a novel pump which is comprised of relatively few parts which are themselves of uncomplicated design, and in which the characteristics of the pumping cycle can readily be altered.
Another object of the invention is to provide a pump having the foregoing features and advantages, in which the constant availability of inflow capacity is insured, and in which the flow passage length and pumping volume are minimized.
Yet another object of the invention is to provide such a pump which is relatively easy to install and disconnect from the subject during surgical procedures.